Vodafone has been forced to issue a grovelling apology to its thousands of followers on Twitter after one of its customer ­service staff broadcast an obscene message on the micro-blogging service.

The message appeared on Vodafone's official Twitter account, which is used by the company to deal with customer complaints. Instead of the usual helpful hints on how to make the most of its range of handsets or direct responses to individual customer service queries, VodafoneUK's 8,824 followers were treated this afternoon to a message reading "VodafoneUK is fed up of dirty homo's and is going after beaver".

Within minutes of the message appearing hundreds of Vodafone customers had contacted the company through Twitter to ask whether its account had been hacked. Despite Vodafone deleting the message from its Twitterfeed, hawk-eyed users of the service saved a copy and were quickly sending it across the internet.

Vodafone was forced to release a stream of apologies, replying to each user individually to say "we weren't hacked. A severe breach of rules by staff in our building, dealing with that internally. We're very sorry". By the evening the company had been forced to release that message to hundreds of individual followers.

"An individual posted an obscene remark on the Vodafone UK Twitter account," said a spokesman for the company. "The individual has been suspended pending further notice."

The "tweet" is understood to have emanated from Vodafone's customer service centre in Stoke, where its web team uses social networking sites such as Twitter to keep in contact with users.

It is just the latest in a growing list of social networking gaffes. As more people sign up to services such as Twitter and Facebook, organisations are having to police their activities as well as maintain their own presence on such sites.

A year ago Virgin Atlantic sacked 13 cabin crew after they used Facebook to call passengers "chavs" and claimed that the airline's planes were full of cockroaches.

Some companies have had their own use of Twitter hijacked by enterprising web users. Last April the Telegraph newspaper set up a so-called "Twitterfall" for its coverage of the budget. The idea was to include any tweets being created on the service that included the tag "#budget". Unfortunately Twitter users spotted that it was unmoderated, and embarrassed the paper and its owners with a stream of tweets such as "Breaking news: Barclay Brothers to pick up your tax bill in unprecedented act of philanthropy. #Budget" – and worse.